Gone are the days of burglars randomly bursting in with ski masks. Today’s criminals will watch and wait until just the right moment before attempting a break-in.

A broken window
Some criminals will throw a rock through a house or car window before even trying to break in, just to see what happens, says Joel Logan, COO of Las Vegas-based Reliance Security. If an alarm goes off and neighbours peer outside to see what’s happening, they might be scared off. But if the homeowners are clearly out of the house or the police never arrive, they might break in that night or soon after. Call the police right away if you’re home, and install motion-sensor floodlights for when you aren’t there, Logan recommends. Check out the 10 hiding spots burglars always look first. 

A strolling stranger
You probably don’t know everyone in your neighbourhood, but a criminal scoping out the area likely won’t just look like an innocent walker. If someone is walking by repeatedly, check their body language, says Logan. “If you take your dog for a walk, you just walk around the neighbourhood. You’re not always checking behind you or looking over your shoulder,” he says. Pay attention to clothing, too. Most people taking a walk for the sake of fitness will be wearing workout gear, so someone in plainclothes who’s out for long periods of time might be up to no good, adds Everett Stern, intelligence director of private intelligence company Tactical Rabbit. Any time you’re feeling uneasy, call the police, he suggests. It’s better to bring them out of their way for a bit than to regret ignoring the warning signs.

An eager photographer
Beyond just looking jumpy, someone watching your home might be taking pictures. They’ll be documenting hiding spots and how close the houses are together – less space between houses means more chance a neighbour will spot them, says Stern. If you notice strangers acting fishy with their cameras, defend yourself by taking your own picture of them, Logan recommends. “You might get into an argument, but if there’s a person with bad intentions, taking a picture of him is a good chance of scaring them off,” he says. And speaking of cameras, here’s the real likelihood that you’re being watched through your laptop camera.

Light bulb problems
Lights are burglars’ enemy,” says Logan. “In lights, they can be seen.” A thief who’s planning to break in might unscrew the bulbs around your house so they don’t turn on and reveal the burglar. Check the bulbs if your lights stop working suddenly. If they’re unscrewed but aren’t burnt out, a thief might be scoping your home, says Logan.

A vehicle that keeps driving by
You don’t need to question every unfamiliar car that drives by, but take note if one passes your house over and over. One with an out-of-state license plate or no plate at all could signal someone is there to watch your neighbourhood, especially if the passengers park the car and don’t get out. Write down the license plate number (if there is one), get a description of the driver or the number of people in the car, and call the police if you’re suspicious, says Logan.

Missing rubbish
A stolen identity can be more valuable than some jewellery and cash. “A lot of burglars won’t enter a home,” says Stern. “They’ll start stealing your garbage.” From there, they’ll rummage around for documents containing any details they can use for stealing your identity, along with what type of job you have or when you’ll be going on holiday. Shred any papers before chucking them to make it harder for crooks to put the pieces together, says Stern. Find out 11 ways that thieves can steal your identity here. 

Untouched mail
An observant criminal will take note when there’s a pile of newspapers building up in front of your house. “When you’re on holiday, that’s a telltale sign you’re not there,” says Stern. When you’re away, ask a neighbour to pick up your papers, pamphlets and anything else signalling no one is home, he suggests.

A missing dog
A barking dog is the last thing a burglar wants when trying to break into your home. If a thief has been scoping your home and is intent on getting in, he or she will let the dog out well before attempting the break-in. “Then they go back in a week or the next day and know the dog isn’t going to alert the neighbours or homeowners,” says Logan. A runaway dog isn’t always the fault of a criminal, but people with bad intentions will use the strategy from time to time.

An empty petrol tank
You could have sworn you had more than a half a tank when you got home last night, but when you left in the morning, the petrol gauge was on empty – and you couldn’t make it to the petrol station in time. There’s a chance a determined burglar drained your tank with a hole or a tube the night before. Now the thief can watch you leave for work, then enter your home without worrying about when you’ll be back.

A moving truck
Criminals rely on the fact that people don’t always know much about their neighbours. While a homeowner is on holiday, they might park a removal truck in the empty driveway – after all, the owners would have taken the car on their trip – then load up without being questioned, says Stern.

Social media posts
Snooping crooks are just one more reason to worry about Internet privacy. “Burglars are using social media now to gather intelligence,” says Stern. “When people post information about their home or a Christmas party, they show different parts of the home or layout.” Especially on image-based platforms like Instagram or Snapchat, robbers could get a sense of where your valuables are to make an efficient theft. Also, avoid posting about your holiday until you’re home. Publicising the fact that you’ll be away for two weeks – leaving your house unattended – opens the door for burglars to feel confident breaking in. Find out 17 things that cyber crooks don’t want you to know here. 

Door-to-door visits
Of course some religious groups or salesmen ring the doorbells with innocent intentions, but some criminals also pose as them to get a look at the inside of your house. Pay attention to how they present themselves. “You talk to them and they don’t know much about the product, or they’re looking around the house more than trying to sell the vacuum cleaner,” says Logan. Your best bet is to play it safe and not open the door, says Stern. Ideally, you’d have a camera and audio system set up so you can see who’s outside your door and communicate with them without opening up. If you don’t, just shout out the door that you aren’t interested, suggests Stern.

A new cleaning person
If you have a cleaning team or other crew that visits frequently, a new person could be a red flag. Burglars might pay off people with access to your house to find out what’s inside, and some might even convince the team to let them pose as part of the crew, says Stern. When a new face shows up, he recommends calling the company and asking who the person is and why he or she is there. If they don’t know whom you’re talking about, it could be a crook.

This article appeared on Reader’s Digest.